The present invention relates to a method for producing a fiber-reinforced thermoplastic resin foamed product including a core layer formed of a thermoplastic resin foamed member, and a surface layer formed of a fiber-reinforced thermoplastic resin sheet.
Elongated products having different shapes in a lateral section and having a foamed layer therein have been used as a constructing material and the like in the same manner as a natural wood material, or as a substitute. For such use, in order to increase the rigidity of the material, a formed product including a core layer formed of a thermoplastic resin foamed member and a surface layer formed of a fiber-reinforced thermosetting plastic resin composite has been used.
Japanese Patent Publication (KOKAI) No. 4-339635 discloses a method, wherein in order to continuously produce a composite having a good mechanical strength with light weight, while continuously supplying a synthetic resin foamed member in one direction, continuous fibers permeated with a thermosetting plastic resin are applied onto an outer surface of the synthetic resin foamed member, which are heated and drawn out to obtain a foamed product.
However, in the method, it is necessary to prepare, beforehand, the foamed member with irregular shape in the lateral cross section. Further, since the foamed product is produced by a draw molding, a resin having a low viscosity is used, so that the thickness of the surface layer and mechanical strength of the foamed product tend to be ununiform. Also, it is difficult to modify and shape the product in a mold.
In view of the above problems, in producing a fiber-reinforced thermoplastic resin foam ed product comprising a surface layer of a fiber-reinforced thermoplastic resin and a core layer of a foamed member, it is an object of the present invention to provide a method for producing a fiber-reinforced thermoplastic resin foamed product having less unevenness in the thickness of the surface layer and an excellent mechanical strength, such as a bending strength.